Dcal
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I'd use zinc under everythingAm I just being stupid? For some reason I thought you couldn't use waterbased on top of solvent based, but just been reading an article that says you should use solvent primer under water topcoat for outdoors water resistance?
Am I just being stupid? For some reason I thought you couldn't use waterbased on top of solvent based, but just been reading an article that says you should use solvent primer under water topcoat for outdoors water resistance?
I'd use zinc under everything
Unless it's on wood.
What type / make of paint is it?
It's hard to get a one coat paint that preforms as well as a primer and top coat.
Epoxy glass flake is about the most durable, however it needs to be applied over a blasted surface, will fade / chalk in sunlight, it's really thick so need expensive airless kit to apply by spraying, (unless you cheat and overthin it) there isn't a wide range of colours and it's not cheap.
With (or without if you don't care about colour fastness) a PU top coat it's hard to beat in extreme conditions like the marine splash zone.
epoxy paint sounds excellent, but I've never tried using it before.Usually the top coat is mostly decorative, the primer and build coats give most of the protection, but there are exceptions.
I would have thought an epoxy would suit all of your needs. The Selemix 7-413 is like an epoxy mastic straight out of the tin but can be thinned down with up to 40% thinners if you want a better finish straight from the gun. You can also apply it with airless kit if you want and it's recommended for wet on wet process, but not if you are putting a waterbased paint over it.
Only slight downside is it needs reasonable prep (like most primers) the Jotun epoxy mastics (and similar) are more forgiving in that respect so it's horses for courses.
Lots of other options in epoxies but the Selemix is hard to beat for the money. (the extra thinning gives a lot of paint per litre)
If I was putting any water based paint over any primer I'd let it cure and give it a sand to be sure of good adhesion, unless there is a system that the paint manufacturer recommends.
Problem with epoxy is it takes an age to dry. Are there any extra fast curing epoxy primers?
Applied thin as wet on wet, but fully cured, wont need much sanding.
epoxy paint sounds excellent, but I've never tried using it before.
Sanding epoxy to apply WBP over the top sounds like a bore, though. I may have to keep looking...
So if i wanted to use epoxy primers I have two options as I see it:If you don’t want to sand do an adhesion test.
Doesn’t need to be complicated.
Make up a puck (could be a bolt with the markings sanded off) and use araldite to stick it to the cured top coat.
You could do a test with wet on wet, primer cured but not sanded and primer cured and sanded.
Let the araldite fully cure and use a lever to pull the puck perpendicular to the surface (try not to twist it)
If the top coat comes off the primer you will know that is the weak spot, if the primer comes off the steel that would tell you you’re prep isn’t good enough.
My guess is the cured and sanded would be best, followed by the wet on wet then the cured and not sanded.
If the three samples are similar, don't bother sanding.
The proper test kit uses hydraulic pressure so gives a reading, but knowing the weak spot is very useful.